1. Field of the Invention
The invention relates to a post-processing unit disposed at a recorded sheet discharge section of an image forming apparatus such as an electronic copying machine that produces recorded sheets of a large size such as drawings. More particularly, the invention is directed to a recorded sheet processing unit for an image forming apparatus which discharges a recorded sheet formed as a rolled sheet by rolling the long recorded sheet in cylindrical form by a sheet rolling unit and by sealing the rolled sheet while sticking an adhesive tape to the rolled sheet by a sealing means.
2. Description of the Conventional Art
Image forming apparatuses for producing recorded sheets by using electrophotographic systems such as electronic copying machines and laser printers use cut sheets of fixed sizes such as A3 and B4 and employ a means for producing recorded sheets by selecting sheets of an appropriate size in accordance with the size of an original. The electronic copying machine carries, at a sheet feed section thereof, a means which accommodates a plurality of sheet feed trays or sheet feed cassettes, selects a type of sheet based on data such as reduction and enlargement rates, and feeds the selected type of sheets toward an image forming section thereof. The recorded sheets produced by the image forming apparatus are discharged toward a discharge tray or the like after being fixed by a fixing unit.
In addition to the electronic copying machine using sheets of small sizes as described above, image forming apparatuses such as electrophotographic copying machines and plotters used for preparing drawings, recorded sheets are often produced by using sheets of such large sizes as A0 and A1. Let us explain a drawing producing image forming apparatus by taking an electronic copying machine as an example. For example, as disclosed in Japanese Patent Unexamined Publication (Kokai) Hei-1-187133/(1989), an apparatus capable of producing recorded sheets of a large size by setting a wide rolled sheet to the sheet feed section and cutting sheets unrolled from the rolled sheet to a size corresponding to an original is used.
However, such large-sized electronic copying machine can discharge recorded sheets to an arbitrary length, whereas the conventional electronic copying machine discharges a long recorded sheet as being a part of the continuous sheet and piles up the discharged sheet as it is in a receiving member such as a large box. For the long recorded sheet such as described above, it is necessary that an operator stands by the recorded sheet discharge section and "rewind" the long recorded sheet. Therefore, the conventional electronic copying machine must be designed so that recorded sheets be put in order so as not to be scattered around the discharge outlet of the image forming apparatus particularly when the long recorded sheets are to be produced.
In addition to the case where the recorded sheets are produced using an original of such a large size as described above, large-sized electronic copying machines of recent development are designed so that an image forming output unit is combined with a computer to constitute a mechanism for discharging recorded sheets of a large size successively based on image data outputted from the output unit. Further, in an electronic copying machine that produces recorded sheets of a large size by connecting an output unit such as a computer to itself, a plurality of output units may be connected to a single electronic copying machine. Therefore, in the case where recorded sheets are produced in accordance with a recorded sheet producing instruction from an arbitrary output unit, an operator must stand by the electronic copying machine at all times; otherwise the recorded sheets are collected in disorder, making a mess with the recorded sheets of a large size scattered around the electronic copying machine.
To overcome the above problem, a unit for folding a recorded sheet of a large size into a fixed size is used in some cases. A recorded sheet folding unit such as disclosed in Japanese Patent Unexamined Publication (Kokai) Sho-63-196462/(1988) or the like may be used. However, a drawing usually prepared by using a plotter or the like has originality and is often used to check and confirm the design to be referred to for recorded sheets. Therefore, the folding unit such as shown in the conventional example is not preferable, hence imposing the problem with respect to how the recorded sheets of a large size are post-processed.
To overcome this problem, such an arrangement as to facilitate the checking of recorded sheets by disposing a sheet rolling mechanism for a discharge tray for discharging recorded sheets is proposed, e.g., in Japanese Utility Model Publication (Kokai) Hei-1-149363/(1989) instead of using the above-described folding unit. This conventional recorded sheet processing unit can simplify post-processing by disposing the sheet rolling mechanism at an end portion of the discharge tray and keeping a long recorded sheet by rolling in cylindrical form. That is, this unit does not involve the operator for rolling the recorded sheet in the course of copying. However, as described above, this unit requires that recorded sheets be taken out of the discharge tray every time a single recorded sheet is discharged even if the mechanism for automatically rolling long recorded sheets is disposed. In addition, a recorded sheet as rolled may be easy to spread out into a single large sheet if not bound or sealed, etc., thereby imposing the problem as to how such a recorded sheet is kept in order. Further, in the case where recorded sheets of a large size are produced successively, the operator must take care of the long original and cylindrical formed sheets every time a single recorded sheet has been prepared, which is a relatively cumbersome operation.
In addition to the above problem, in the case where recorded sheets are to be produced successively with the image forming apparatus being implemented by a high-speed electrophotographic copying machine or the like, the recorded sheets are discharged from the apparatus close to each other. Therefore, the performance of the image forming apparatus would not be satisfactory unless the post-processing unit has an adequate processing capacity. Further, if the sheet rolling unit is used as the post-processing unit, it is required that the opening and closing member be returned after a rolled sheet has been formed and discharged from the sheet rolling unit and before a next recorded sheet is threaded into the sheet rolling unit. It is for this reason that development of a unit that can meet such requirement has long been needed.
As described above, in the case of arranging the rolled sheet sealing mechanism; e.g., even in the case of arranging a means for sealing with an adhesive tape, it is necessary to make the adhesive tape supplying mechanism simple in structure. A conventional rolled sheet sealing unit employs only a device for rolling the entire circumference of the rolled sheet with the tape. However, the use of such a long adhesive tape entails inconvenience in handling the recorded sheet at the time of unrolling the recorded sheet. Further, the use of such a long tape is disadvantageous in terms of cost and time; the taping operation is time-consuming.